The third torque your body must produce in order for you to run your best will come from the right arm. So, looking at the right arm on our female track athlete in Figure 1 below, imagine it is the only force acting on the body. So, nothing else is going on. The other arm isn’t involved and neither are the legs. We see, then, that because it has been thrust out in front of her, which is a function of the shoulder, or, arm flexor muscles, it will exert a pulling force on the right shoulder joint, forward, in this direction as depicted by the white horizontal arrow.
And yes, there is a vertical component to this force, as well, that I have shown by the red arrow in Figure 2 below.
But as before, I am going to illustrate the net result of these two components with just one simple horizontal white arrow. Now, again, if this was the only force acting on the body, do you think the effect of it would be to just pull her straight forward, or, do you think there might also be some additional reaction?
Well, once more, the only way this force causes her to move straight ahead would be if it were acting along her midline, as seen in Figure 3, but that’s not the case.
So, since it’s displaced away from the midline, It would not only pull her forward, but would also cause her upper body to twist, or, rotate.
Again, It would have to, because it does not fall along her midline where her center of gravity lies and perhaps you starting to see a pattern with this. So, if she does rotate, the question then, is, which direction would it be? Clockwise, or, counterclockwise? To help you see this better, let’s look at this from above on our male athlete.
The same force on our female athlete pulling forward on her right shoulder joint can also be shown here on our male athlete in Figure 5 below.
So, as the force pulls forward on this vertical line that now represents the level of his shoulders, we can see where it will try and rotate it in the… what direction? Care to take a guess? If you said the counterclockwise direction, then good job, once more as you are correct and let’s show it by the direction of this red arrow in Figure 6 below.
And let’s also go ahead and place the corresponding counterclockwise arrow showing this rotational force, or, torque on our female track athlete and perhaps now you can envision this one taking place better, too.
So, this is the third torque your body must produce in order for you to run your best. Now let’s move on to Torque #4.